This application is a 371 of PCT/DE98/02693 filed Sep. 04, 1998.
The present invention relates to a low voltage circuit breaker having a contact arrangement, a drive mechanism for actuating the contact arrangement, an actuating shaft for transmitting a drive force from the drive mechanism to the contact arrangement, and a bearing arrangement accommodating the actuating shaft.
Low voltage circuit breakers have a plurality of components that are adapted to different partial functions and are connected to one another during the manufacture of the circuit breaker. The largest components or units are the switching poles, i.e., contact systems that include stationary and movable switching contacts, with their support insulation and components for connecting to a drive mechanism common to a plurality of such switching poles. The movement provided by the drive mechanism is transmitted to all existing contact systems via an actuating shaft supported at a fixed point. Formerly the actuating shaft was considered as a component of the drive mechanism from the design point of view.
An example of this design is described in German Patent No. 44 16 088, which shows a lever arrangement having a conventional design for transmitting a drive force. It has parallel support plates and limiting parts attached thereto, which reduce the distance between the support plates to an appropriate value for guiding the articulated levers. The hinge pins of the levers are slidingly guided on the limiting parts.
German Patent Patent 44 16 090 shows a bearing arrangement for an actuating shaft of a multipole electrical switchgear having a bearing mechanism formed by parallel walls and having shaft bearings with half-shells. In German Patent No. 42 27 352 there is illustrated an actuating shaft common to the pole units formed from the switching chambers, which is formed from shaft segments corresponding to the pole units. The pole units rest on a support, which is dimensioned according to the largest width of the pole units. Further illustrations of force transmission systems for actuating switching contacts are described in German Patent No. 28 35 879 and German Patent No. 27 26 489. All these described designs have proven to facilitate the manufacture of the individual components, but they have the disadvantage that their function cannot be tested until the circuit breaker is fully assembled.
This means that, from the mechanical point of view, if a defect is found in a fully assembled circuit breaker, it is difficult to determine which component is defective. Ultimately the fully assembled components must be disassembled in order to replace the defective component.
An object of the present invention is to facilitate testing and reduce the time needed for troubleshooting. In particular, a test of whether the path provided by the drive yields the contact force needed for regular closing of the contact arrangements is to be performed.
This object is achieved according to the present invention by the fact that the bearing arrangement for the actuating shaft has at least one bearing body connected to a pole component accommodating the contact arrangement.
The xe2x80x9cswitching polexe2x80x9d component thus becomes fully operational by itself and can be tested in a simple manner before the circuit breaker is fully assembled. Furthermore, there are no disadvantages to the standalone testability of the drive mechanism.
According to one example embodiment of the present invention, the actuating shaft is integrated in the xe2x80x9cswitching polexe2x80x9d component by using at least three bearing bodies, the central main bearing body having conventional elements, in particular springs for providing a retaining force, end stops, a chatter limiter and elements for absorbing residual energy. This central main bearing body is advantageously connected to one wall of the pole component via a combination of positive and non-positive attachment elements. These may advantageously be two or more plug-in bases in conjunction with the respective pocket holes in the wall of the pole component, and centering journals with internal threads that align the central main bearing body with respect to the pole component wall and the drive mechanism. Near its ends, the actuating shaft is supported by two auxiliary bearing bodies, which are fastened in the same manner or in similar manners, but which have only part or none of the above-mentioned additional functions. The manufacture and assembly of the actuating shaft can be facilitated by dividing the actuating shaft into two symmetric segments. These segments are driven synchronously via a coupling pin traversing the lever mounted on both segments of the actuating shaft. The advantage of the two-part actuating shaft is that each of the segments is supported at two bearing points. The type of support is thus statically determined and can therefore be implemented with little play. Any possible alignment error is compensated via the coupling without affecting the friction characteristics.
The main bearing body with an abutment for retaining springs, which maybe molded onto the main bearing body to form a single piece. The retaining springs can be mounted on the main bearing body prior to the assembly of the bearing arrangement. The retaining springs are thus arranged in a compact manner and advantageously engage the actuating shaft lever as a dead center or super-dead center system. This reduces the reaction on the main energy storage device of the switching drive.